Landscaping and lawn maintenance crews use high-powered rotary, string cutters for the rapid removal of grass, weeds, brush and other low height vegetation growing around fence posts and other stationary objects. The string element is hard, but flexible enough to bend when it strikes an object more solid than the vegetation. It is very efficient in cutting grass and weeds, however in the process it strikes softer objects than the string itself, like a wooden fence post, and in the process, removes or chips away small pieces of the surface with the result that costly repairs are required. The land owner having many wooden fence posts "eroded" to the point of weakening the post is required to periodically replace each post over time.
This has become more of a problem as rotary string cutters have become more powerful. High-powered edgers, some of which are capable of generating rotary velocities in excess of 9,000 RPM's and the torque output of a 2 cycle, 2 horsepower engine, produce a flailing force sufficiently large to cut one inch brush and other heavy vegetation at ground level.
In the past, preventing the undesirable growth of vegetation around trees, along fence lines or next to other structures has largely focused on attempting to inhibit the growth of the vegetation rather than protecting the structure. One version includes a ring which lays flat on the ground and extends radially out from the tree at its base. The object is to prevent the growth of grass within a radius adjacent the tree trunk, not to protect the tree trunk from damage by string cutters.
Moreover these barrier devices are made of rather thin, flexible plastic materials which would disintegrate under the forceful attack of high powered edgers.
In addition, these barrier devices are expensive to manufacture, difficult to install, not especially attractive when installed and require repeated maintenance which has not led to their being adopted in any widespread commercial sense.
A vegetation barrier of the type referred to is disclosed in U.S. Pat. No. 3,571,972 issued Mar. 23, 1971.